Guess you've never seen a magic show then huh? Slight of hand does exactly that, make it harder to effectively observe one hand because the other draws your attention..... Common sense doesn't cover everything.
Originally Posted by Triple_Se7en
Common sense says its easier for camera security to watch one hand movement on video - versus two hands.
Originally Posted by Uphill_Both_Ways
I had no idea that holding a basket in one hand prevents everyone from pocketing a can of tuna with the other.